PARIS - Salty water just below the surface of Mars could hold enough oxygen to support the kind of microbial life that emerged and flourished on Earth billions of years ago, researchers reported Monday (Oct 22).
In some locations, the amount of oxygen available could even keep alive a primitive, multicellular animal such as a sponge, they reported in the journal Nature Geosciences.
"We discovered that brines" - water with high concentrations of salt - "on Mars can contain enough oxygen for microbes to breathe," said lead author Vlada Stamenkovic, a theoretical physicist at the Jet Propulsion Laboratory in California.
"This fully revolutionises our understanding of the potential for life on Mars, today and in the past," he told AFP.
Up to now, it had been assumed that the trace amounts of oxygen on Mars were insufficient to sustain even microbial life.
"We never thought that oxygen could play a role for life on Mars due to its rarity in the atmosphere, about 0.14 per cent," Stamenkovic said.
By comparison, the life-giving gas makes up 21 per cent of the air we breathe.
On Earth, aerobic - that is, oxygen breathing - life forms evolved together with photosynthesis, which converts CO2 into O2. The gas played a critical role in the emergence of complex life, notable after the so-called Great Oxygenation Event some 2.35 billion years ago.
But our planet also harbours microbes - at the bottom of the ocean, in boiling hot springs - that subsist in environments deprived of oxygen.
"That's why - whenever we thought of life on Mars - we studied the potential for anaerobic life," Stamenkovic.
LIFE ON MARS?
The new study began with the discovery by Nasa's Curiosity Mars rover of manganese oxides, which are chemical compounds that can only be produced with a lot of oxygen.
Curiosity, along with Mars orbiters, also established the presence of brine deposits, with notable variations in the elements they contained.
A high salt content allows for water to remain liquid - a necessary condition for oxygen to be dissolved - at much lower temperatures, making brines a happy place for microbes.
Depending on the region, season and time of day, temperatures on the Red Planet can vary between minus 195 and 20 deg C.
The researchers devised a first model to describe how oxygen dissolves in salty water at temperatures below freezing.
A second model estimated climate changes on Mars over the last 20 million years, and over the next 10 million years.
Taken together, the calculations showed which regions on the Red Planet are most likely to produce brine-based oxygen, data that could help determine the placement of future probes.
"Oxygen concentrations (on Mars) are orders of magnitude" - several hundred times - "greater than needed by aerobic, or oxygen-breathing - microbes," the study concluded.ros hommerson Patent Leather Marty Black FlatCLARKS NEW COLLECTION WOMENS SHOES SIZE 9-1/2LifeStride BLACK SHOES WOMENS SIZE 8 1/2 WSBICCA of California Brown Faux Leather Slip On Casual Loafer Flats Shoe 8WAnne Klein Women's Kamy Leather Loafer Flat, Gold Leather, Size 5.0Mojari Indian Women Shoes Ethnic Handmade Jutti Leather Ballerinas Flat US 5/7 , Jutti US 5-10 Traditional Handmade Leather Indian Women Shoes Ballerinas , Frye Slip On Driving Shoe Size 7.5 Women's Brown Leather Moc Toe Slipper , SANUK DONNA MIXED UP LEOPARD FLORAL SIDEWALK SURFER SHOES, US 7/ ~NWTEcco Loafer Black Leather Monk Strap Buckle Flat Walking Shoes Womens Size 8.5MLifeStride Womens dee Suede Closed Toe Black Size 5.5 , Keds Taylor Swift Collection Floral Lilac Purple Size 11 / 41 Women's Shoes , CIVIC DUTY Sensation SNEAKERS Ladies size 9 M Lime Tyvek Hi Top Shoes New in BoxSanita Professional Clog Women size 41 US 10 10.5 Black , Josef Seibel Brown Leather Hook Loop Strap Closure Loafers 39 / 8-8.5Vans Off the Wall Womens Surf Striped Aqua Boat Shoes 9Womens Saucony Grid Phantom Running Shoes Size 8M (Z306)Women's NIKE Downshifter 5 Black Pink Running Walking Athletic Shoes Size 9 , Women's Adidas Liquid Ride Shoes Sneakers Size 9.5 Running Black Green Blue G11 , Mirak Celia Ruiz 300 Wide Fit Summer / Womens Shoes (FS354)Wolverine Women's Gazelle CSA STSP Safety Approach Shoe Black Size 8M , 12A2 APL Running Walking Athletic Jogging Training Cross Women's Shoes Size 7.5ADIDAS ZX FLUX W WHITE B2262 ATHLETIC RUNNING SNEAKERS WOMEN'S SIZE 8.5 NEW WOB , Nike WMNS Air Jordan 1 Retro Low NS Black Gold lot AH7232 011 Womens Size 6Marc Fisher Women's Alie Flat Black Patent Leather FlatsSuperga Women's 2790 Cotmetu Fashion SneakerWOMENS NIKE AIR MAX FURY SZ 7.5 PURE PLATINUM SAIL AA5740 007 , DIMMI WALK SNEAKERS SHOES 6.5 LEATHER TRAIL HIKING COMFORT DEEP BLUE FLAT , T.U.K. Unisex Fashion Sneaker- Pick SZ/Color.Under Armour Spine RPM Storm Gray Pink Running Shoes 1238325-019 Women’s Size 7
"Our results do not imply that there is life on Mars," Stamenkovic cautioned. "But they show that the Martian habitability is affected by the potential of dissolved oxygen."